Composition of matter



Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE COMPOSITION OF MATTER Wilhelm Martin, Oberbruch, Bez. Aachen, Germany, assignor to North American Rayon Gorporation, New York, Delaware N. Y., a corporation of 2 Claims.

This is a division of my co-pending application Serial No. 77,897, filed May 4, 1936, now U. S. Patent No. 2,159,391.

This invention relates to an improved method of polishing foraminous devices but particularly has for its object the polishing of spinnerettes or spinning nozzles which are used in the manufacture of filaments or threads of artificial origin.

In the manufacture of spinnerettes for use in the extrusion of artificial filaments the first step in the process is the stamping out of the body of the spinnerette in the form of a cylinder closed at one end and having an outwardly extending annular flange at the other end. The closed end is called the draw plate and is that part of the spinnerette which has the extrusion openings formed therein through which the spinning solution is expressed or extruded.

The openings in the draw plate are usually made by forming hollow imperforate projections in the said draw plate. The point of the inner surface of the hollow projection extends below the plane of the outer surface of the draw plate so that when the projection is subsequently removed by any suitable means, such as grinding it off, an opening appears. These openings are then punched from the opposite side and the spinnerette is then ready for the final step in the manufacture thereof.

The spinnerettes used are usually made from precious metals and it is necessary to polish them after the holes have been formed therein. As is well known in the art, the polishing of spinnerettes has a decidedly important effect upon the satisfactory operation of the spinnerette during the spinning process in the manufacture of artificial silk filaments. It is during the polishing step that the openings of the draw plate are frequently irremediably injured due to thin ridges being found in the openings, or the edges of the openings may be polished oif completely. The results of the polishing operation, therefore, often means a defective spinnerette.

It is a well known fact that satisfactory spinning may be obtained only from a spinnerette which has been properly polished and which has perfect openings formed in the draw'plate.

It is therefore one object of the present invention to devise an improved method of polishing spinnerettes which will not harm the extrusion openings formed therein.

Another object of the present invention is to devise a method whereby the extrusion openings are protected during the polishing operation.

These and other objects will in part become obvious and will in part be pointed out in the following specification and appended claims.

According to the present invention it has been found that the openings in spinnerette nozzles may be preserved in perfect condition during the polishing operation, if the openings prior to polishing are filled up with a solid, bubbleless, nonbrittle, but correspondingly hard substance which possesses the quality of protecting the edges of the spinnerette openings during the said polishing operation, and which may be completely removed from the said openings after the spinnerettes have been completely polished.

As filling material for the above purpose a mixture of borax and litharge melted together has proven to work exceptionally well.

The proportions of the two substances may be varied, but for gold-platinum alloy spinnerettes a mixture of 7 borax and litharge has given the best results.

The filling of the spinnerette openings takes place in the molten state, i. e., the openings are filled with the melted mixture which is then allowed to harden therein.

After the spinnerettes have been polished to a high lustre with the polishing agents ordinarily used for this purpose, the solid filling substances maybe easily and readily removed by any suitaable means, such as by means of heated strong nitric acid.

Modifications of the above process will be readily recognized by those skilled in the art to which it relates and it is therefore desired to include all those modifications falling within the scope of the appended claims.

What I claim is:

1.,A composition of matter for filling the openings of precious metal spinnerettes consisting of a fused mixture of litharge and borax.

2. A composition of matter for filling the openings of gold-platinum alloy spinnerettes consisting of a fused mixture of one part by weight of litharge and two parts by weight of borax.

WILHELM MARTIN. 

